In many applications in optics a uniform intensity distribution across a light beam is required. The light emitted by most lamp and laser sources does not have a flat intensity profile. As a result, some sort of optical system must be employed to uniformize a beam. One especially important class of light sources is excimer lasers, which have recently been shown to be very attractive for high resolution lithography, an application that typically requires the beam to have a uniform intensity distribution to better than within .+-.5%. U.S. Pat. No. 3,660,778 to LeBlanc, Sr. discloses a corner reflector laser beam folding device. A laser beam is reflected parallel to the incident beam and increasing the time duration the laser spends in the lasing medium, thereby producing a beam with increased power. IBM Technical Disclosure Bulletin Vol. 24 No. 11A, April 1982, page 5368 discloses a wedge-shaped acrylic light guide used to illuminate a liquid display. The wedge causes multiple internal reflections to concentrate the light on the display surface. Myer in Applied Optics, Vol. 10 No. 9, pages 2179-2182 (1971) describes the use of mirrors forming a cone for replicating images. It reports that a plane parallel mirror tunnel will replicate images in an orthogonal pattern whereas a cone mirror tunnel will replicate images in a virtual spherical pattern. None of the references describes the use of beam folding to increase beam uniformity and to sharpen edge definition.